All-fiber coherent beam combiners based on the self-imaging effect can achieve a near-perfect single laser beam,which can provide a promising way to overcome the power limitation of a single-fiber laser.One of the key...All-fiber coherent beam combiners based on the self-imaging effect can achieve a near-perfect single laser beam,which can provide a promising way to overcome the power limitation of a single-fiber laser.One of the key points is combining efficiency,which is determined by various mismatches during fabrication.A theoretical model has been built,and the mismatch error is analyzed numerically for the first time.The mismatch errors have been numerically studied with the beam quality and combining efficiency being chosen as the evaluation criteria.The tolerance of each mismatch error for causing 1%loss is calculated to guide the design of the beam combiners.The simulation results are consistent with the experimental results,which show that the mismatch error of the square-core fiber is the main cause of the efficiency loss.The results can provide useful guidance for the fabrication of all-fiber coherent beam combiners.展开更多
Self-imaging is an important function for signal transport,distribution,and processing in integrated optics,which is usually implemented by multimode interference or diffractive imaging process.However,these processes...Self-imaging is an important function for signal transport,distribution,and processing in integrated optics,which is usually implemented by multimode interference or diffractive imaging process.However,these processes suffer from the resolution limit due to classical wave propagation dynamics.We propose and demonstrate subwavelength optical imaging in one-dimensional silicon waveguide arrays,which is implemented by cascading straight and curved waveguides in sequence.The coupling coefficient between the curved waveguides is tuned to be negative to reach a negative dispersion,which is an analog to a hyperbolic metamaterial with a negative refractive index.Therefore,it endows the waveguide array with a superlens function as it is connected with a traditional straight waveguide array with positive dispersion.With a judiciously engineered cascading silicon waveguide array,we successfully show the subwavelength self-imaging process of each input port of the waveguide array as the single point source.Our approach provides a strategy for dealing with optical signals at the subwavelength scale and indicates functional designs in high-density waveguide integrations.展开更多
A fast and simple method to extract phase-contrast images from interferograms is proposed, and its effectiveness is demonstrated through simulation and experiment. For x-ray differential phase contrast imaging, a stro...A fast and simple method to extract phase-contrast images from interferograms is proposed, and its effectiveness is demonstrated through simulation and experiment. For x-ray differential phase contrast imaging, a strong attenuation signal acts as an overwhelming background intensity that obscures the weak phase signal so that no obvious phase-gradient information is detectable in the raw image. By subtracting one interferogram from another, chosen at particular intervals,the phase signal can be isolated and magnified.展开更多
We investigate the Airy–Talbot effect of an Airy pulse train in time-dependent linear potentials.The parabolic trajectory of self-imaging depends on both the dispersion sign and the linear potential gradient.By impos...We investigate the Airy–Talbot effect of an Airy pulse train in time-dependent linear potentials.The parabolic trajectory of self-imaging depends on both the dispersion sign and the linear potential gradient.By imposing linear phase modulations on the pulse train,the Airy–Talbot effects accompanied with positive and negative refractions are realized.For an input composed of stationary Airy pulses,the self-imaging follows straight lines,and the Airy–Talbot distance can be engineered by varying the linear potential gradient.The effect is also achieved in symmetric linear potentials.The study provides opportunities to control the self-imaging of aperiodic optical fields in time dimension.展开更多
文摘All-fiber coherent beam combiners based on the self-imaging effect can achieve a near-perfect single laser beam,which can provide a promising way to overcome the power limitation of a single-fiber laser.One of the key points is combining efficiency,which is determined by various mismatches during fabrication.A theoretical model has been built,and the mismatch error is analyzed numerically for the first time.The mismatch errors have been numerically studied with the beam quality and combining efficiency being chosen as the evaluation criteria.The tolerance of each mismatch error for causing 1%loss is calculated to guide the design of the beam combiners.The simulation results are consistent with the experimental results,which show that the mismatch error of the square-core fiber is the main cause of the efficiency loss.The results can provide useful guidance for the fabrication of all-fiber coherent beam combiners.
基金The authors acknowledge the financial support from the National Key R&D Program of China(2017YFA0303701,2016YFA0202103)National Natural Science Foundation of China(91850204,11674167).Tao Li acknowledges support from Dengfeng Project B of Nanjing University.The authors have no conflicts of interest to disclose.
文摘Self-imaging is an important function for signal transport,distribution,and processing in integrated optics,which is usually implemented by multimode interference or diffractive imaging process.However,these processes suffer from the resolution limit due to classical wave propagation dynamics.We propose and demonstrate subwavelength optical imaging in one-dimensional silicon waveguide arrays,which is implemented by cascading straight and curved waveguides in sequence.The coupling coefficient between the curved waveguides is tuned to be negative to reach a negative dispersion,which is an analog to a hyperbolic metamaterial with a negative refractive index.Therefore,it endows the waveguide array with a superlens function as it is connected with a traditional straight waveguide array with positive dispersion.With a judiciously engineered cascading silicon waveguide array,we successfully show the subwavelength self-imaging process of each input port of the waveguide array as the single point source.Our approach provides a strategy for dealing with optical signals at the subwavelength scale and indicates functional designs in high-density waveguide integrations.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61101175,61571305,and 61227802)
文摘A fast and simple method to extract phase-contrast images from interferograms is proposed, and its effectiveness is demonstrated through simulation and experiment. For x-ray differential phase contrast imaging, a strong attenuation signal acts as an overwhelming background intensity that obscures the weak phase signal so that no obvious phase-gradient information is detectable in the raw image. By subtracting one interferogram from another, chosen at particular intervals,the phase signal can be isolated and magnified.
基金supported by the National Natural Science Foundation of China(Nos.11674117 and 11974124)。
文摘We investigate the Airy–Talbot effect of an Airy pulse train in time-dependent linear potentials.The parabolic trajectory of self-imaging depends on both the dispersion sign and the linear potential gradient.By imposing linear phase modulations on the pulse train,the Airy–Talbot effects accompanied with positive and negative refractions are realized.For an input composed of stationary Airy pulses,the self-imaging follows straight lines,and the Airy–Talbot distance can be engineered by varying the linear potential gradient.The effect is also achieved in symmetric linear potentials.The study provides opportunities to control the self-imaging of aperiodic optical fields in time dimension.
